The present disclosure relates to a controller and control method for an internal combustion engine. The controller and the control method control an internal combustion engine that includes an exhaust purifying device, which purifies exhaust gas discharged from the cylinders, and fuel injection valves provided for the respective cylinders.
For example, Japanese Laid-Open Patent Publication No. 2016-31050 discloses a controller that executes dither control. In the dither control, when there is a requirement for an increase in the temperature of a catalyst device (exhaust purification device), at least one of the cylinders is treated as a rich combustion cylinder, in which the air-fuel ratio is richer than the stoichiometric air-fuel ratio, and the remaining cylinders are treated as lean combustion cylinders, in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio.